Error: SELECT r.t0, cl.pmname as clinic, r.pmname as roomname, t.subject AS tcname, c.* FROM course AS c LEFT JOIN roomcate AS r ON c.room=r.pmid LEFT JOIN clinicate as cl ON cl.pmid = r.clinicid LEFT JOIN teacher AS t ON c.t_serno=t.serno WHERE c.serno=0 AND c.status = 1;